1. Field of Invention
This invention relates generally to the subject of methods and systems of providing cooling to a cabinet or enclosure. The cooling is needed because the cabinet contains electronic components that generate heat. Such cabinets are used in a variety of devices, for example servers, and switching and routing devices used in telecommunications, and in Telephone Company, Internet service provider, and computer network applications. More particularly, the invention relates to a cabinet design that includes an internal air-to-air heat exchanger and fan arrangement that provides cooling for the cabinet while simultaneously preventing dust, humidity or pollutants from the environment from entering the interior of the cabinet where the electronic components are located. This feature is particularly important in the application of electronics cabinets used in outside environments, such as in the case of some types of switching and networking equipment where the cabinets can be located next to roads, on telephone poles and in other harsh environments.
2. Description of Related Art
Integrated telecommunications devices, such as routers, switches, network access servers, remote access concentrators, TI span termination shelves, DSL access multiplexers, and other similar types of devices, often take the form of a medium or large size enclosure or cabinet. The cabinet, sometimes referred to in the art as a “chassis” or “shelf”, typically incorporates one or more printed circuit boards or, more commonly, modular cards, with such cards typically being capable of being manually inserted into and removed from the chassis. These printed circuit boards and/or cards incorporate numerous semiconductor-based electronic components such as microprocessors and integrated circuit chips, which generate significant amounts of heat during operation.
Integrated circuit chips, microprocessors, and other similar electronic components are designed to operate within a particular temperature window. Accordingly, the heat generated by such components must be removed from the enclosure they are housed in or else the components will overheat and fail. It is known in the art to provide air flow features by which relatively cooler ambient air is conducted into the chassis, and relatively warmer air generated inside the chassis is exhausted from the chassis though an aperture in the chassis housing, typically using one or more fans. Representative patents addressing cooling and air flow considerations within an electronics device include the following references: Manes, U.S. Pat. No. 4,502,099, Garner, U.S. Pat. No. 4,648,007 and the patents to Gourdine, U.S. Pat. Nos. 5,297,005 and 5,422,787. Gourdine's patents describe a cabinet or chassis in which one or more electronic components are individually isolated and subject to separate airflow in order to maximize the cooling of all the components in the cabinet. The patent to Stockbridge, U.S. Pat. No. 6,301,108, describes a chassis cooling arrangements using ambient air as well as a safety feature in the form of a fire-containment trap door that closes off the ambient air passages in the event of a fire in the chassis.
Cooling arrangements for electronics cabinets using separate air-to-air heat exchangers are known in the art and such products are available from Thermacore. See, for example the following papers: Jon Zuo, Ron Hoover and Fred Phillips, “Advanced Thermal Architecture for Cooling of High Power Electronics”, Thermacore International, Inc., 2001; Nelson J. Gernert, “Cooling of Power Semiconductors in Cabinets”, Thermacore International, Inc., 2001; and, Z. J. Zuo, E. H. Dubble and S. D. Garner “Compact, Double Side Impingement, Air-To-Air Heat Exchanger”, Thermacore, Inc., undated, all of which are available from the Thermacore.com website. A separate air-to-air heat exchanger, such as the HXi Series air-to-air heat exchanger from Thermacore, is expensive and increases the size of the overall system, and thus does not fully address the problems in the art.
The present invention provides an advantage over known systems by integrating the heat exchanger function within the walls of the cabinet, whereby a lower cost, smaller package is produced. Moreover, preferred aspects of this invention provide for air-to-air heat exchange without introducing outside air (which may contain dust, humidity or pollutants) into the interior of the cabinet.